The present invention relates to an apparatus for the preparation of a thin film and, in particular, to an apparatus for the manufacture of a thin film, which can improve the distributions of, for instance, thickness, quality and composition of the resulting thin film on the surface of a wafer (or a substrate) when a film is formed according to the CVD technique such as the MOCVD technique.
Up to now, there have been proposed various kinds of techniques such as that for uniformly admixing a raw gas and a reactive gas; that for appropriately rotating a wafer to be processed during the formation of a film; and that for uniformly injecting gases onto the wafer through a shower head of a film-forming chamber, as means for improving the plane uniformity in the distributions of, for instance, thickness, quality and composition of the resulting thin film on the surface of a wafer, when a thin film is prepared according to the CVD technique, for instance, the MOCVD technique.
In the production of a thin film according to the MOCVD technique, it is common that a gas mixture comprising a vaporized raw material and a reactive gas is introduced into a film-forming chamber maintained at a vacuum and a vapor phase reaction of the gas mixture is induced on a substrate to be processed, which is placed on a stage disposed within the film-forming chamber to thus form a desired film on the substrate. On the top face of the film-forming chamber, a shower head is arranged, while it is opposed to the stage and a gas-mixing chamber is connected to the upstream side of the shower head. Upon the formation of a film according to such an MOCVD technique, the raw gas and the reactive gas fed to the gas-mixing chamber are admixed together therein and then introduced into film-forming chamber, which has been evacuated to a predetermined degree of vacuum, through the shower head in the form of a gas mixture having a predetermined and desired mixing ratio and the chemical reaction of these gases is induced on the substrate surface to thus form or deposit a film thereon.
The foregoing various kinds of conventional techniques proposed for the preparation of a thin film having uniform distribution of quality and thickness of a film thus formed on a substrate cannot be decisive means for solving the problems concerning the formation of a thin film, on a substrate, having, for instance, good uniformity in the quality and distribution of thickness, because of, for instance, the complicated structure of the currently used MOCVD apparatus and the difficulty in the formation of a uniform gas mixture. For this reason, there has been desired for the development of a CVD apparatus, which has a simple structure and which can variously be controlled so as to be in agreement with a variety of film-forming conditions.